Robin (Cobie Smulders) does a story on "Love Solutions", a matchmaking service boasting a 100% success rate, and she and Barney (Neil Patrick Harris) recommend Ted (Josh Radnor) try it out. He is not interested, believing it to be "giving up," but Barney tricks Ted into going anyway. Ellen Pierce (Camryn Manheim), the woman in charge of the matchmaking service, sees immediately that Barney is only seeking a one-night stand with a desperate woman (the alias he wrote on the registration form, "Jack Package," gives him away), but promises she "can work with" Ted. Ted is skeptical, but Ellen calculates that out of all the women in New York City, there are only eight whom Ted can date; facing this daunting statistic, Ted readily agrees to try it. Ellen promises success within three days, but after five days and no results, Ted wants to go back to find out what the problem is. Everyone tells him not to "Ted out" about it (explaining that Ted's name is also a verb, which means to over-think). Still, he returns to Love Solutions, only to find Ellen, alone and despondent, telling him he is unmatchable. Ted spies one that is a 9.6/10 match, but she has already been matched. Undaunted, Ted finds out she is a dermatologist and makes an appointment to see her, only to find that she is engaged and will be getting married in a few days. He tells her that if things change, he'll be available; she calls him up, but only to inform him that he has a cancerous mole on his back. He blurts out that they are a 9.6, and she tells him to not believe in matchmaking statistics. Ted returns to Love Solutions, and finds that Ellen has become distraught over believing to have failed in finding Ted's perfect match. However, Ted still has hope he will find "the one", and she can help him keep searching, no matter how long it takes.
Meanwhile, Marshall (Jason Segel) and Lily (Alyson Hannigan) discover an unusual creature in the apartment. When they first see it, Lily thinks it is a cockroach, while Marshall thinks it is a mouse. Either way, it scares them so bad they run to the bar and Lily drinks heavily to forget. When they spot it again they try to kill it with bug spray and a phone book, but when the phone book starts moving, they run off again. Having gotten a better look, they now describe the creature as having six legs, antennae, and an exoskeleton, but also has tufts of fur, whiskers, and a tail, and roughly the size of a potato. Marshall and Lily call it the "cockamouse." Robin is skeptical of them, but eventually they catch it, and Marshall takes it to the Columbia University Biology department, but discovers it has escaped and is still at the apartment. Robin finally sees the creature and throws a drink at it, as the only way she can think of subduing it is by trying to get it drunk. Marshall arrives and throws it out the window, and to their surprise the "cockamouse" flies away.